It is possible to drive from one to the other as service tunnel at Folkestone to Calais is more than capable of taking vehicles.
OK, try driving Dortmund to Wembley thru your service tunnel!
The train being referred to as a "rolling road"
, what's a cross channel ferry, a "floating road"? ... And I guess that a hovercraft is/was a "flying road" and a seacat is a "dual carriageway"